After the Swans' victory over St Kilda in Wellington last Thursday, the playing group flew back to Sydney the following day, with some then travelling on to Melbourne for some time off.
There was a 10-day break between the Saints game and the Swans' next fixture, against the Brisbane Lions at the SCG this Sunday.
Mumford went out on the Friday night and indulged a little too much, leading to him being asked to leave more than one establishment.
The club wouldn't reveal the exact nature of Mumford'spunishment, with the ruckman maintaining his place in the side this week, but coach John Longmire confirmed he had been disciplined.
"Yeah there was an incident last week and we dealt with it internally a couple of days ago," Longmire said on Thursday.
"Going into a long week, Shane went to Melbourne and had a couple of drinks and we dealt with it with our captains and spoke to Shane about it and dealt with it in the players' code of conduct.
"We’re not going to go into details of what he was fined, (but) it's disappointing for any player.
"It was disappointing from Shane's point of view and he acknowledged that."
It is a rare slip-up for a club that prides itself on its discipline and practices on and off the field, but Longmire was confident it was a one-off.
"All footy clubs have players that make mistakes," he said.
"We're confident that he'll work through his mistakes and learn from it and push on."
In better news for the premiers, 2010 first round draft pick Jed Lamb will finally make his debut this week.
The 20-year-old, who has been plagued by injuries in his brief career, can play as a small forward and through the midfield.
"It's exciting for him, he's really earned that opportunity that he'll get this week," Longmire said.
"He's been injured and had a couple of years of really hard battles in regards to injury and that's really set him back and set his development back.
"But over the pre-season he's taken some big steps forward, he's been able to get some continual training in and really taken a big step up.
"I think he's a really good story, Jed Lamb. He's really popular among the group and they're really rapt to have him in the team."
Lamb could only look on as fellow 2010 draftees Luke Parker and Alex Johnson became premiership players and he is understandably relieved his chance has come.
"I can't wait," he said.
"It has been frustrating. My first year I missed a lot of football after injuring my hamstrings and last year I had some shin splints, but towards the back end I started to build some consistency.
"I've just been working hard and luckily I get my chance this week."
